1. Field of the Invention
The present invention relates to an information device such as a notebook personal computer having a plurality of antennas that vary in polarization characteristics or directivity characteristics.
2. Description of the Related Art
In radio communication, a receiving antenna often adopts a diversity system to take measures against fading.
Two diversity systems are well known: one is a space diversity system in which two antennas are arranged in view of a distance between them, and the other is a polarization diversity system in which two antennas are arranged in view of an angle between them.
For example, Jpn. Pat. Appln. KOKAI Publication No. 2000-114848 discloses an antenna using a diversity system. The feature of the antenna lies in that two patch antennas are arranged on an insulating substrate symmetrically with respect to a point at a distance of a three-fourths wavelength of a transmit/receive frequency. These two antennas adopt a diversity system.
There may be a case where polarization components of transmitted waves vary among radio communication devices of communication partners and, in this case, it is desirable to configure a space diversity system by antennas capable of receiving high-level polarization components. If the levels of horizontal polarization components received by two antennas are both high, these antennas are used as horizontally polarized antennas to configure a space diversity system. In some cases, a right-side antenna can be operated as a horizontally polarized antenna and a left-side antenna can be operated as a vertically polarized antenna.
As described above, in order to secure a wide communication-capable range, the configuration of a diversity antenna can flexibly be varied according to the antenna polarization characteristics of radio communication devices of communication partners.
In the above publication, however, one of the space diversity system and the polarization diversity system has to be chosen. This causes a problem that a considerably wide communication-capable range cannot be attained.
Under the circumstances, it is desired to provide an information device having a wide communication-capable range as a diversity antenna.